1#define BDNZ BC 16,0, 2#define BDNE BC 0,2, 3 4/* 5 * mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) 6 * 7 * diff[0:alen-1] = a[0:alen-1] - b[0:blen-1] 8 * 9 * prereq: alen >= blen, diff has room for alen digits 10 * 11 * R3 == a 12 * R4 == alen 13 * R5 == b 14 * R6 == blen 15 * R7 == diff 16 * R8 == temporary 17 * R9 == temporary 18 */ 19TEXT mpvecsub(SB),$-4 20 21 MOVW alen+4(FP),R4 22 MOVW b+8(FP),R5 23 MOVW blen+12(FP),R6 24 MOVW diff+16(FP),R7 25 SUB R6, R4 /* calculate counter for second loop (alen > blen) */ 26 SUB $4, R3 /* pre decrement for MOVWU's */ 27 SUB $4, R5 /* pre decrement for MOVWU's */ 28 SUBC $4, R7 /* pre decrement for MOVWU's and set carry */ 29 30 /* skip subraction if b is zero */ 31 CMP R0,R6 32 BEQ _sub1 33 34 /* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */ 35 MOVW R6, CTR 36_subloop1: 37 MOVWU 4(R3), R8 38 MOVWU 4(R5), R9 39 SUBE R9, R8, R8 40 MOVWU R8, 4(R7) 41 BDNZ _subloop1 42 43_sub1: 44 /* skip subtraction if a is zero */ 45 CMP R0, R4 46 BEQ _subend 47 48 /* diff[blen:alen-1] = a[blen:alen-1] - 0 + carry */ 49 MOVW R4, CTR 50_subloop2: 51 MOVWU 4(R3), R8 52 SUBE R0, R8 53 MOVWU R8, 4(R7) 54 BDNZ _subloop2 55_subend: 56 RETURN 57 58